This invention relates to a methanation reactor. More particularly, the present invention relates to a methanation reactor which has, inserted therein, a heat exchanger for preheating the cold gases to be sent to the catalytic reaction.
Methanation reactors are known: they are vertical cylindrical holders which contain in their interior one or more layers of a catalyst. Their operation, summarized concisely, is as follow: the hot gases to be methanized enter the reactor at a temperature of about 300.degree. C., flow through the catalyst bed, wherein they are reacted, and exit the reactor at a temperature of about 350.degree. C. The hot gaseous mixture thus obtained is sent to an external heat exchanger so as to preheat to about 300.degree. C. the cold gases to be sent to methanation.
The methanation reactor constructed according to the conventional technology has the disadvantage that it causes the hot gases to be reacted to contact the reactor casing for a certain time and this fact makes it compulsory to work under low pressures or to construct the reactor casing of very expensive types of stainless steels, or to use refractory linings for shielding such casing from the direct contact with the gases. The latter approach involves a further increase in initial costs because, due to the considerable thickness of the linings, the size of the reactors must consequently be enlarged.
It has surprisingly been found, by virtue of the present invention, that the same results can be obtained, from the point of view of the methanized products, by using a reactor having a tube-bundle heat exchanger inserted therein, which is positioned beneath the toroidal catalyst bed, and by adopting a circulation of cold gases to be reacted within the gap between the reactor casing and the catalyst bed-heat exchanger assembly.